Configure API token using LinodeClient{}.SetToken(...) rather than transport; allow configuring LINODE_CA

[lgarber-akamai]

📝 Description

This pull request updates the linodego.Client creation logic to set the user-configured API token using the LinodeClient{}.SetToken(...) function rather than using a custom oauth2 transport. This allows the LINODE_CA environment variable to be specified without any additional logic to set the trusted root CA, which is necessary because linodego can only modify an HTTP client's trusted CAs if the user-provided client's RoundTripper is a *http.Transport.

✔️ How to Test

The following test steps assume you have pulled down this PR locally, have Ansible installed, have an SSH public key exported under ~/.ssh/id_rsa.pub, and have a valid Linode API token exported under the LINODE_TOKEN environment variable.

Integration Testing

1. Run the following command to kick off the integration tests:

make int-test

Manual Testing

TODO

[yec-akamai]

The change looks good! However, we probably need to update the test case a bit. I ran the integration test but got current image used to create linode is not valid anymore: https://github.com/linode/docker-volume-linode/blob/main/integration-test/test.yaml#L38

I updated the image to use linode/ubuntu24.04 locally and it passed!

[lgarber-akamai]

The change looks good! However, we probably need to update the test case a bit. I ran the integration test but got current image used to create linode is not valid anymore: https://github.com/linode/docker-volume-linode/blob/main/integration-test/test.yaml#L38

I updated the image to use linode/ubuntu24.04 locally and it passed!

Nice find! I can address that in this PR

[zliang-akamai]

Test works well, nice work!